Does debarking intensity during the first cork extraction affect future cork thickness?

The use of increasing debarking during the first harvest of cork oak trees (Quercus suber L.) had no effect on the secondary cork calliper (thickness) in one of the trials and had a small negative effect in a second trial. Little evidence was found that debarking coefficient is a useful index for the management of cork oak stands.

Context. The Portuguese national legislation defines, without the support of scientific data or knowledge, maximum values of debarking coefficients (ratio of debarking height and perimeter at breast height measured over cork). For the first debarking, this value is limited to 2.0.
Aims. The aim of this study was to determine the impact of increasing cork debarking coefficient on the calliper of the secondary cork extraction.
Methods. Trees were located in two sites, in distinct regions characterized by low or high productivity classes. Three debarking coefficients were considered: 1.5, 2.0 and 2.5. The debarking coefficient for the first cork extraction was randomly selected for each tree. During the second debarking, a cork sample was taken from each tree. The samples were used for assessing secondary cork calliper. Differences in cork calliper were analysed using both correlation analysis and modelling approaches.
Results. Debarking intensity increase had a small negative effect on secondary cork thickness in the most inland site, while no effect was detected in the more coastal site.
Conclusion. In our experiment, debarking intensity had a significant but small effect in one site and no effect in other sites. Debarking coefficients not only should be defined according to legal constraints but also instead should be adapted considering tree and site characteristics.

Keywords
Quercus suber L., Montado, Debarking coefficient, Debarking height, Secondary cork, Cork thickness, Cork calliper

Publication
Paulo, J.A. & Tomé, M. Annals of Forest Science (2017) 74: 66. https://doi.org/10.1007/s13595-017-0662-x

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